The value of arterial velocity waveform analysis, in detecting and assessing the severity of atherosclerotic occlusive disease of peripheral and extracranial arteries, will be investigated by determining the extent to which factors other than luminal narrowing effect the waveform, exploring methods for improving the quality and reproducibility of waveform recordings, determining the most discriminating yet cost effective method of waveform analysis, and comparing this method with competitive non-invasive methods of diagnosing arterial occlusive disease in patients with angiographically documented lesions.